Reuters cited sources last week as saying that Britain was likely to announce an order soon for 14 of the advanced jets, marking Britain’s first firm F-35 purchase since it committed to buying 48 planes in 2012.

“We are moving towards that point,” Hammond said when asked if he could confirm the imminent order.

“We will have to place a firm order very soon in order to have the first squadron ready to start flying training off the ‘Queen Elizabeth’ in 2018, which is our current plan,” he said in an interview with Reuters Television during the Munich Security Conference.

The Queen Elizabeth is one of two British aircraft carriers currently under construction.

He declined to confirm that the order would be for 14 planes “because we haven’t completed the process, but we will be making an announcement in due course”.

Britain is expected to order the F-35 B vertical take-off variant of the Joint Strike Fighter.

It has so far taken delivery of three training jets.

The F-35, considered to be the world’s most expensive weapons programme at $396 billion so far, was designed to be the next-generation fighter jet for the U.S. Air Force, Navy and Marines.

It is being built by the United States, Britain and seven other co-development partners - Italy, Turkey, Canada, Australia, Denmark, Norway and the Netherlands.

British companies such as BAE Systems (BAES.L) and Rolls Royce (RR.L) build 15 percent of each F-35 aircraft.

Hammond said he was not worried by reports of technical issues that could delay the F-35’s entry into service.

A U.S. Defense Department report last week warned that software, maintenance and reliability problems with the stealth fighter could delay the U.S. Marine Corps’ plans to start using its F-35 jets by mid-2015.

“This is a complex weapons procurement programme. There are always issues in the development of weapons like this, and this particular report comes in a long and well-established line of highly critical reports about weapons systems when they are at this stage of their development,” Hammond said.

“The whole point of this internal appraisal is to highlight where the issues still are that need to be resolved in the programme. It is part of the process and it shouldn’t be seen as a negative part of the process at all,” he said.

Britain’s Conservative-led government was embarrassed by its flip-flop two years ago on which variant of the radar-evading aircraft to buy, a decision which cost the British taxpayer at least 74 million pounds ($123 million).